1. Field
This disclosure relates generally to RF devices, and more specifically, to an RF power transistor device with a large periphery Metal-Insulator-Silicon shunt capacitor and method thereof.
2. Related Art
RF transistor designs have traditionally included an integrated shunt capacitor design; however, the traditional integrated shunt capacitor has poor RF performance. In other words, such a traditional integrated shunt capacitor design degrades the RF power transistor's power, gain and efficiency. Such degradation in RF power transistor performance is especially noticeable in high power RF power transistor plastic package designs.
In a known high power RF device, wires and on-chip high Q metal-insulator-metal (MIM) shunt capacitors are used to achieve input and output matching of the high power RF devices. However, such MIM shunt capacitors are fabricated on a separate chip which has a refractory metal substrate. Accordingly, the MIM shunt capacitors are incompatible, and cannot be integrated, with LDMOS silicon based processes.
Furthermore, quality factor of a shunt capacitor is an important characteristic of an RF LDMOS power amplifier device. However, quality factor of devices that employ conventional rectangular shunt capacitor layouts is in need for improvement. That is, conventional rectangular shunt capacitor layouts for silicon substrates, specifically higher resistivity substrates, have resulted in lower Q capacitors.
Accordingly, there is a need for an improved method and apparatus for overcoming the problems in the art as discussed above.